The field of the disclosure relates generally to data readers, and in particular, to hybrid autofocus systems for data readers operable to optimize active and passive autofocus techniques for improving data reading functions.
Generally, an autofocus optical system uses one or more sensors, control systems, and a motor to focus a selected point or region. Autofocus systems used with electronic devices, such as cameras and data readers, may be separated into two general classes—active autofocus systems and passive autofocus systems. Active autofocus systems measure distance to the target item independently of the optical system, and subsequently adjust the optical system for correct focus. These systems may measure distance in a variety of ways, such as by using rangefinders to emit ultrasonic sound waves and measuring the delay in their reflection, or by using infrared light to triangulate the distance to the object/item.
Passive autofocus systems, on the other hand, determine correct focus by performing passive analysis of the image that is entering the optical system, instead of using sound waves or otherwise directing energy toward the item. Passive autofocusing may use a variety of techniques for analyzing the image, such as phase detection or contrast detection. Phase detection may be achieved by dividing the incoming light into pairs of images and comparing the images to each other. Contrast detection autofocus may be achieved by measuring contrast through the lens within a sensor field, and comparing the intensity difference between adjacent pixels to correct image focus.
Typically, active autofocus systems provide a fast distance measurement and are able to focus the electronic device in a shorter period of time as compared to a passive autofocus system. However, active autofocus systems tend to be less precise than passive autofocus systems, especially when the field-of-view includes multiple moving items located at varying distances from the device. Some electronic devices have sought to address these inherent weaknesses by using a hybrid autofocus system that combines active and passive autofocus techniques. However, the inventors have found that these prior hybrid systems fail to provide optimal performance in data-reading environments that typically have multiple moving items in the field-of-view of the device. In addition, many modern autofocus camera systems are based on phase detection technology that requires costly and specialized image sensors equipped with specific phase-detection pixels.
Accordingly, the present inventors have recognized a need for an improved hybrid autofocus system for data readers that combines both active autofocus and passive autofocus techniques to provide an optimized data reader capable of handling complex fields-of-view and operating in a data-reading environment. In addition, the present inventors have recognized a need for such an improved hybrid autofocus system operable without reliance on phase detection technology. Additional aspects and advantages will be apparent from the following detailed description of example embodiments, which proceeds with reference to the accompanying drawings.
Understanding that the drawings depict only certain embodiments and are not, therefore, to be considered limiting in nature, these embodiments will be described and explained with additional specificity and detail with reference to the drawings.